Znorg. Chem. 1993, 32, 3640-3647
3640
Photochemically Induced Reversible CO Insertion into Ruthenium-Amido Bonds' Olaf C. P. Beers, Jos G. P. Delis, Wilhelmus P. Mul, Kees Vrieze, and Comelis J. Elsevier' Anorganisch Chemisch Laboratorium, Universiteit van Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
Wilberth J. J. Smeets and Anthony L. Spek Bijvoet Center for Biomolecular Research, Vakgroep Kristal- en Structuurchemie, Universiteit Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands Received October 8, 1992 Upon photolysis of Ru2(C0)6(MeC=C(H)CH2N-i-Pr) (1) and Ruz(CO)6{RCC(H)N-t-Bu) (2a,R = i-Pr; 2b, R = PhCHz) under an atmosphere of CO, insertion of CO into the Ru-N bond of the amido ligands takes place, affording Ru2(CO),{MeC=C(H)CH,N(i-Pr)C(O)}(3)and Ruz(CO)a{RCC(H)N(t-Bu)C(O))(4a/b). The X-ray crystal structures of 3 and 4a have been determined. Crystals of 3 are triclinic, space group P i , a = 8.733(1) A, b = 12.841(2) A, c = 17.261(2) A, LY = 82.79(1)O, /3 = 77.95(1)', y = 72.48(1)', 2 = 4, convergence reached at R = 0.058 for 6028 reflections with Z > 2Su(Z). Crystals of 4a are monoclinic, space group P2,/n, a = 8.222(1) A, b = 17.877(1) A, c = 13.592(1) A, /3 = 99.34(1)O, Z = 4, convergence reached at R = 0.026 for 3665 observed reflections with Z > 2.5u(I). The photolysis of 2a with PPh3, yielding the PPh3-substituted analogue of 4a, Ru2(CO)s(PPh3){RCC(H)N(t-Bu)C(0)j (6a) revealed that the inserted CO ligand is coordinated to the metal prior to insertion. The same isomer of complex 6a has also been prepared by initial thermal substitution of CO by PPh3 in 2a, yielding RU~(CO)~PP~~{RCC(H)N-I-BU) (Sa), and its subsequent photochemical reaction with CO. R u ~ ( C O )+~R-C(H)=C(H)C(H)=N-R' ~
Introduction The classic insertion of carbon monoxide into a metal-carbon bond is an important reaction-step in stoichiometricand catalytic organometallic chemistry.28 The mechanism of insertion has been studied extensively and it is now generally accepted to occur by the migration of a metal-attached alkyl or aryl group to a ciscoordinated CO ligand.2 The insertion of CO into a transition metal-amido bond is less often enco~ntered.~ A few examples have been reported in the chemistry of the actinides, where the rather strong metal-oxygen interaction, which is usual for this type of metals, probably facilitates the migratory insertion of carbon monoxide into the metal-amido bond.4 In general, amido complexes of the platinum group metals are not very susceptible to CO insertion. Instead, in reactions with CO, often ligand substitution or addition takes place.3 An exception has been encountered for Pt(PhzPCH2CH*PPhz)(CH3)(NHCHzPh), featuring preferentially insertion of CO into the metal-amido bond. This reaction is particularly interesting, because in the starting complex both a M-C and a M-N bond, in which insertion may take place, are present. Although CO insertion into metal-amido bonds is rather uncommon, it has been proposed to occur during the conversion of Schiff bases into phtalimidines, which is either catalyzed by cobalt596 or by iron in the stoichiometric reaction between Fez(C0)g and Schiff bases upon oxidation of the resulting amidotype product with FeC13.' Recently, CO insertion into a Co(1) Reactions of Monoazadieneswith Metal Carbonyl Complexes. 17. For other parts see refs 10, 1 1 , and 26. (2) (a) Parshall,G.W. Homogeneous Catalysis;Wiley-Interscience: NewYork, 1980; Chapter 5. (b) Koga, N.; Morokuma, K. J . Am. Chem. SOC.1986,108,6136. (c) Calderazzo, F. Angew. Chem. 1977,89, 305. (3) Fryzuk, M. D.; Montgomery, C. D. Coord. Chem. Rev. 1989, 95, 1 . (4) Fagan, P. J.; Manriquez,J. M.; Vollmer, S. H.; Day, C. S.;Day, V. W.; Marks, T. J. J. Am. Chem. SOC.1981,103, 2206. (5) Murahashi, S.; Horrie, S. Bull. Chem. SOC.Jpn. 1960, 33, 247. (6) Rosenthal, A. In Organic Synthesis via Meral Carbonyls; Wender, I., Pino, P., Eds.; Wiley: New York, 1968; Vol l., p 433. (7) Bagga, M. M.; Flannigan, W. T.; Kno, G. R.; Pauson, P. L.; Preston, F. J.; Reed, R. I. J . Chem. SOC.C 1968, 36.
0020- 166919311332-3640$04.00/0
I90.120"C
A
H
OC-RU
co 2am R' = iPr. R = CH3
-
a : R' = t h , R = iPrb : R'
t-Bu, R = Ph-CHZ-
Figure 1. Formation of 1 and 2 by cyclometallation of a monoazadiene on the Ru-carbonyl skeleton.
amido bond was proposed to take place in the Co2(CO)~-catalyzed carbonylation of azetidines, yielding pyrrolidinones.8 Another example of CO insertion into a metal-amido bond as part of a complex reaction sequence, has been provided by the 1,3-dipolar cycloaddition reaction of alkynes with metal-heterodiene complexes, whereby 1,S-dihydropyrrol-2-ones are formed stoichiometrically.9 In our study of the reactivity of monoazadienes R C ( H ) y C (H),C(H)i,=NR' toward RU~(CO)IZ, we have encountered two dinuclear complexes 1 and 2 (Figure l), which are the first isolable products of the thermal reaction.1° By replacement of the @-hydrogen atom of the MAD ligand by a Me group, the cyclometalation path leading to the five-membered metallacycle in 1 is blocked. In this case the reaction of RuS(C0)12 with MAD gives high yields of 2a.11 Complexes 1 and 2 possess fiveand four-membered azametallacycles, respectively. The bonding (8) Roberto, D.; Alper, H. J . Am. Chem. SOC.1989, 111, 7539. (9) de Lange, P. P. M.; Friihauf, H.-W.; van Wijnkoop, M.; Vrieze, K.; Wang, Y.; Heijdenrijk,D.; Stam, C. H. Organomerallics 1990,9,1691. (10) (a) Mul, W. P.; Elsevier, C. J.; Polm, L. H.; Vrieze, K.; Zoutbcrg, M. C.; Heijdenrijk, D.; Stam, C. H. Organomerallics 1991,10,2247. (b) Elsevier, C. J.; Mul, W. P.; Vrieze, K. Inorg. Chim.Acta 1992,200,689. (c) Polm, L. H.; Elsevier, C. J.; Mul, W. P.;Vrieze, K.; Christophersen, M. J. N.; Muller, F.; Stam, C. H. Polyhedron 1988, 7 , 2521.
0 1993 American Chemical Society
Inorganic Chemistry, Vol. 32, No. 17, 1993 3641
CO Insertion into Ruthenium-Amido Bonds of the nitrogen atom in these complexes can be best described as that of a bridging amido function (vide infra) but alternatively one may invoke the presence of an azaallyl moiety.IOC Both complexes exhibit fluxionality of the ligand system involving interchange of the T - C and ~ a-Ccoordination."-' In this article we report the photochemically induced CO insertion into the Ru-amido bond of both 1 and 2. During our investigations in this area, the synthesis of the diiron analogue of 2 and its reaction with CO have been published by Mirkin et
Table I. Crystal Data for Complexes 3 and 4.
3
a,
A
b, A c, A
a,deg
8, deg
al,12,13
7, deg
Experimental Section
T, K A, A
v,A3
1H and 13C(1H)NMR spectra were recorded on Bruker AC 100 and AMX 300 spectrometers. The 13C NMR spectra were recorded using an APT pulse sequence. IR spectra were measured on Perkin-Elmer 283 and Nicolet 7199B FTIR (liquid nitrogen cooled, Hg, Cd, Te detector) spectrophotometers using matched NaCl solution cells of 0.5-mm path length. Field desorption (FD) mass spectra were obtained with a Varian MAT71 1 double focussing mass spectrometer with a combined EI/FI/ FD source, fitted with a 10-pm tungsten wire FD-emitter containing carbon microneedles with an average length of 30 pm, using emitter currents of 0-15 mA. Elemental analyses were carried out by Dornis und Kolbe, Mikroanalytisches Laboratorium, MUlheim a.d. Ruhr, Germany. All preparations were carried out under an atmosphere of purified nitrogen. Carefully dried solvents were used. Silica gel for column chromatography (Kieselgel60,70-230 mesh, E. Merck, Darmstadt, Germany) was dried before use. Photochemical experiments were performed with a high-pressure mercury lamp in combination with a Pyrex cut-off filter (A 1 300 nm) and water cooling. The complexes Ru~(CO)~(M~C~(H)CH~N (1)Io - I -and P ~ Ru~(CO)~(RCC(H)N-?) Bu) (29,R = i-Pr; 2b, R = PhCH2)IOJ1 were prepared according to literature procedures. Reported FD-mass date are based on the highest peak of the isotopic pattern of the molecular ion, which corresponds to Io2Ru (calculated value in parentheses). Synthesisof Ru2(CO)~MeC+C(H)CHfl(kPr)C=O) (3). A solution (1; 240 mg, 0.5 mmol) in 50 mL of RU~(CO)~(M~C=C(H)CH~N-~-FV) of hexane was irradiated under an atmosphere of CO at 25 OC for 8 h. During this period the color of the solution changed from pale yellow to yellow-orangeand a small amount of a red product, which was identified as [Ru(CO)& by IR~pectroscopy,~~precipitated. The reactionproducts were separated by column chromatography on silica. With hexane as the eluent 70 mg of unreacted 1 (30%) was obtained. Subsequent elution with hexane/diethyl ether (19:l) afforded 10 mg of Ru2(CO)6{MeCC(H)C(H)N=C(Me)zJ (5%).15 With hexane/diethyl ether (1:l) as the (3, eluent the yellow complex RU~(CO)~(M~C=C(H)CH~"(~-P~)D=O) 80 mg, 30%) was obtained. Crystals of 3 suitable for X-ray diffraction were obtained from a saturated hexane solution cooled at -30 OC. Anal. Found (calcd) for 3: C, 33.01 (33.01); H, 2.54 (2.57); N, 2.80 (2.75); FD-mass: m / e 510 ( M = 511). Synthesis of
Ruz(CO)'(RCC(H)N(t-Bu)C=O) (4.1 R = APK 4b, R
= PbCHZ). A pale yellow solution of 2a/b (0.20 mmol) in 50 mL of hexane was irradiated under 1.2 bar of CO. After 8 h the IR spectrum of the resulting light-yellow solution showed quantitative conversion of 2 into 4. In order to remove traces of impurity the product was chromatographed on silica. Elution with hexane/diethyl ether (19:l) yielded complex 4 in 9C-95% yield. Crystals of 4a suitable for X-ray diffraction were obtained from a saturated hexane solution at -30 OC. Anal. Found (calcd) for 4a: C, 35.77 (35.76); H, 3.22 (3.16); N, 2.44 (2.61). Found (calcd) for 4b: C, 40.97 (41.04); H, 2.92 (2.90); N, 2.43 (2.39). Synthesis of Ru2(CO)@Ph~(kPr-CC(H)N-t-Bu) (Sa). A solution of 2a (0.10 g, 0.2 mmol) and PPh3 (0.05 g, 0.2 mmol) in 50 mL of heptane was refluxed for 4 h. The resulting yellow-orangesolutionwas transferred to a silica column. Elution with hexane/dichloromethane (2: 1) yielded (11) Mul, W. P.; Elsevier, C. J.; Vuurman, M.;Smeets, W. J. J.; Spek, A.
L. To be published.
(12) Mirkin, C. A.; Lu, K.-L.; Geoffroy, G. L.; Rheingold, A. L.; Staley, D. L. J. Am. Chem. SOC.1989, I l l , 7279. (13) (a) Mirkin, C. A.; Lu, K.-L.; Snead, T. E.; Young, B. A.; Geoffroy, G. L.; Rheingold, A. L.; Haggerty, B. S. J. Am. Chem. SOC.1991, 113, 3800. (b) Mirkin, C. A.; Oyer T. J.; Wrighton, M.S.;Snead, T. E.; Geoffroy, G. L. J. Am. Chem. SOC.1992,114, 1256. (14) Hastings, W. R.; Baird, M. C. Inorg. Chem. 1986, 25, 2913. (15) Mul, W. P.; Elsevier, C. J.; Vrieze, K.; Smccts, W. J. J.; Spek, A. L. Organometallics 1992, 11, 1891.
space group Z Dx,g ~ m - ~ p, cm-1 R' RWb
8.733(1) 12.841(2) 17.261(2) 82.79( 1) 77.95(1) 72.48( 1) 1801.1(4) 295 0.710 73 Pi (No. 2) 4 1.879 16.8 0.0580 0.0798
'R UIFd - IFd)/EPd.
49
8.222( 1) 17.877(1) 13.592(1) 90 99.34( 1) 90 1971.3(3) 295 0.710 73 P 2 l / n (No. 14) 4 1.811 15.4 0.026 0.040
Rw = (Ew(lFd - IFd)2/IwPd2J1/2.
the yellow complex Sa (0.10 g, 0.14 mmol,70%). Anal. Found (calcd): C,51.55 (51.50);H,4.25 (4.30);N, 1.93 (1.90). FD-mass: m/e745 (M = 745). Synthesis of Ru2(CO)QPh~(kPrCC(H)N(t-Bu)C=O)(6a). I. A solution of 0.10 g of 59 (0.14 mmol) in 40 mL of hexane and just enough THF to obtain a clear solution (about 3 mL) was irradiated under 1.2 bar of CO for 8 h. The resulting solution was chromatographed on silica with CH2Cl2 as the eluent, affording the yellow complex 6a in 0.08 g yield (74%). II. A solution of 0.10 g of 2a (0.2 mmol) with 0.05 g of PPh3 (0.2 mmol) in 50 mL of hexane was irradiated for 4h. After workup (vide supra) complex 6a was isolated in 0.13 g yield (85%). FD-mass: m / e 773 (M= 773). Thermal Conversion of Complex 3/4/6 into 1/2/5. A solution of 3, 4, or 6 (0.1 mmol) in 20 mL of hexane was stirred at 60 OC for 3 h. During this period quantitative conversion into the complexes 1, 2, or 5, respectively, took place as observed by spectroscopic techniques (IR, 'H NMR). When the same experiment was performed under 1.2 bar of CO, no reaction was observed. NOEDifference Experiment for the Complexes 51 and 6a. NMR tubes containing solutions of Sa and 6.in CDCl3 were prepared, taking standard precautions for NOE-difference measurements. When the proton resonances of the PPh3 group in the 'H NMR spectrum of 59 and 6a were saturated, in the case of 59 a NOE was observed at the methine resonance of the i-Pr group. For 6. as well a NOE was observed at the i-Pr group but in this case on the Me resonance at 0.89 ppm. Low-Temperature IR Experiment with Complex 2% In a lowtemperature IR cell, a solution of 2a in THF (A5 mM) was cooled to -100 OC and the IR spectrum was recorded @-scale: 0-1.4 absorbance). After irradiation for 10 min at -100 OC the IR spectrum was recorded again. The results aredepicted in Figure 7. Then the solution wasallowed to warm to room temperature and the IR spectrum now showed again the absorptions of the parent complex 2a with about the same intensities as compared to the starting situation. CrysWStructureDeterminationof3aad 4a. X-ray data were collected on an Enraf-Nonius CAD4 diffractometer (Mo Ka, Zr filtered, X = 0.710 73 A). Crystal data are collected in Table I. Both structures were solved with standard Patterson and Fourier techniques (SHELXS86I6) and refined on F by full-matrix least-squares techniques. Neutral atom scattering factors were taken from ref 17 and corrected for anomalous dispersion.'* All calculations were performed with SHELX76I9 and PLATON20 (geometrical calculations and illustrations) on a MicroVAX cluster. Positional parameters are listed in Tables I1 and 111. Ru2(CO)~{MeC=C(H)CHfl(I-pr)C=O) (3). Data were collected for a brownish rod-shaped crystal mounted on top of a glass fiber. Unit cell parameters were determined from a least-squares treatment of the SET4 setting angles of 25 reflections with 11.3 < 6' < 14.1'. The unit (16) Sheldrick, G. M.SHELXS86. Program for crystal structure determination. University of Gbttingen,Federal Republicof Germany, 1986. (17) Cromer, D. T.; Mann, J. B. Acra Crysrallogr. 1968, A24, 321. (18) Cromer, D. T.; Liberman, D. J . Chem. Phys. 1970, 53, 1891. (19) Sheldrick, G. M. SHELX76. Crystal structure analysis package. University of Cambridge, England, 1976. (20) Spek, A. L. Acra Crysrallogr. 1990, A46, C34.
3642 Inorganic Chemistry, Vol. 32, No. 17, 1993
Beers et al.
Table II. Final Coordinates and Equivalent Isotropic Thermal Parameters of the Non-Hydrogen Atoms of Ru2(C0)6(MeC=C(H)CHzN(iPr)C=O) (3) z atom X Y U(eq), A2 Ru(1) 0.66476(10) 0.76604(6) 0.10317(4) 0.0424(3) 0.iaoszisj 0.68047i6j o.o466(3j R U ~ jZ 0.94968i 1oj 0.5484(5) 0.2465(4) 0.062(3) 0(1) 0.7237(9) 0.7814(7) -0.0673(5) 0.092(4) O(2) 0.8313(13) 0.9584(7) 0.0745(6) 0.098(4) O(3) 0.3770(11) 0.5672(8) 0.0747(7) 0.127(6) O(4) 0.5543(15) 0.7476(10) 0.0436(7) 0.124(5) O(5) 1.2263(13) 0.6025( 7) 0.3022(5) 0.08 l(4) O(6) 1.1238(11) 0.4663(7) 0.0838(5) 0.114(5) O(7) 1.0230(14) 0.7386(5) 0.2345(4) 0.039(2) N(l) 0.6050(9) 0.9369(9) 0.0825(7) 0.075(5) C(l) 0.8704(16) 0.8554(8) 0.1341(6) 0.051(3) C(2) 0.7960(12) 0.8415(8) 0.2140(6) 0.056(4) C(3) 0.8011(13) 0.2709( 5 ) 0.8153(7) 0.048(3) C(4) 0.6588(13) 0.2767(6) 0.7216(9) 0.058(4) C(5) 0.4458(12) 0.26 lO(8) 0.078(5) 0.8123(10) C(6) 0.3044(12) 0.3660(7) 0.6974( 11) 0.084(5) C(7) 0.4444( 15) 0.2240(5) 0.6361(7) 0.043(3) C(8) 0.7494( 11) -0.0025(6) 0.7759(7) 0.064(4) C(9) 0.7737(16) 0.0860(6) 0.8848(9) 0.062(4) C(10) 0.4796(13) 0.0862(7) 0.6403(9) 0.066(4) C(11) 0.5911(15) 0.0876(7) 0.7270( 12) 0.083(5) C( 12) 1.1228(16) 0.2473(6) 0.057(4) 0.6326(9) C(13) 1.0635(12) 0.1096(6) 0.080(5) 0.5481( 11) C(14) 1.0012(15) a
U(eq)= one-third the trace of the orthogonalized U.
Table 111. Final Coordinates and Equivalent Isotropic Thermal Parameters of the Non-Hydrogen Atoms of Ru~(Co)6li-PrCC(H)N(r-Bu)c~} (49) Ru( 1) Ru(2) O(1) O(2) O(3) O(4) O(5)
O(6) O(7) N C(l) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C( 14) C(15) C(16) a
-0.25505(3) -0.02542(3) 0.2767(4) 0.0891(4) -0.2519(4) -0.5395(3) 42183(4) -0.4927(3) 0.2042(3) -0.0233(3) 0.0306(4) 0.1980(4) 0.0398(6) -0.0905(5) 0.0853(4) -0.1082(4) -0.1341(4) -0.2242(5) -0.3415(8) -0.0979(6) 0.1631(5) 0.0470(4) -0.1669(5) -0.4346(4) -0).2327(4) -0.4015(4)
0.26485( 1) 0.15297( 1) 0.07496(18) 0.14975(18) 0.01474( 18) 0.15910( 19) 0.3006(2) 0.39324(17) 0.28479(15) 0.30393( 13) 0.38346(16) 0.3788(2) 0.4292(2) 0.4202(2) 0.25488(17) 0.25952(17) 0.18465( 17) 0.1330(2) 0.1707(3) 0.0843(3) 0.10224( 19) 0.15066( 19) 0.0649(2) 0.1994(2) 0.2868(2) 0.34639( 19)
0.58 156(2) 0.5827l(2) 0.6932(3) 0.3780(2) 0.5357(3) 0.5188(3) 0.3676(2) 0.6086( 3) 0.5869(2) 0.66958( 17) 0.7012(2) 0.7684(3) 0.6070(3) 0.7604(3) 0.61 16(2) 0.7310(2) 0.7028(2) 0.7659(3) 0.8241 ( 5 ) 0.8326(4) 0.6504(3) 0.4529(3) 0.5533(3) 0.5419(3) 0.4462(3) 0.6035(3)
0.0371( 1) 0.0385(1) 0.0846( 12) 0.0726( 10) O.O9Oa( 13) 0.0791 (1 1) 0.0756(13) 0.0755( 10) 0.0586(9) 0.0362(7) 0.0428(9) 0.0567(11) 0.0662( 13) 0.0583( 11) 0.041 l(9) 0.04 1O ( 9 ) 0.0399(9) 0.055 1(1 1) 0.101 (2) 0.0860( 19) 0.0542( 11) 0.0490( 11) 0.0553( 11) 0.0527(11) 0.0494( 11) 0.051 l(l1)
U(eq)= one-third of the trace of the orthogonalized U.
cell parameters were checked for the presence of higher latticesymmetry?1 Reflection profiles were rather broad, the crystal was found to be twinned, and data collection was performed on one of the superimposed twinlattices. The intensities of 8787 reflections were corrected for Lp, for small linear decay (2.9%) of the intensity control reflections during the 5 0 h of X-ray exposure time, and for absorption (using the DIFABS method:' correction range 0.81-1.22) and merged into a unique set of 6041 reflectionswithI> 2.5a(Z). Hatoms wereintroducedoncalculated positions (C-H = 0.98 A) and included in the refinement riding on their carrier atoms with one common isotropic thermal parameter (U = 0.074(7) A2). All non-hydrogen atoms were refined with anisotropic (21) Spek, A. L. J. Appl. Crysrallogr. 1988, 21, 578. (22) Walker, N.; Stuart, D. Acra Crysrallogr. 1983, A39, 158.
IPr, ~ > R u ~ N ~ ~ R & o
hexane
o
c
3
2a/b
CH,
CO
OC-RU
oc
I
ru.
co
I
--
: R IPr Ph-CHT
b:R
Figure 2. Photochemically induced reactions of 1 and 2 with CO. thermal parameters. Thirteen reflections with Fo >> Fc were excluded from the final weighted refinement cycles; convergence was reached at R = 0.0580. Ru2(Co)diPrCC(H)N(t-&)M) (4r). Data were collected for a yellow plate-shaped crystal glued on top of a glass fiber. Unit cell parameters were determined from a least squares treatment of the SET4 setting angles of 25 reflections in the range 14 < B < 17O. The intensities of 491 1 reflections were corrected for Lp and for absorption (Gaussian integration; correction range 1.21:1.80) and merged into a unique set of 3672reflectionswithD 2.5u(I). Hatomswereintroducedoncalculated positions (C-H = 0.95 A) and included in the refinement riding on their carrier atoms with two common isotropic thermal parameters. Seven strong low-order reflections were excluded from the final weighted refinement cycles, convergence was reached at R = 0.026.
RCMllts
Formation of the Complexes. Upon irradiation of Ruz(C0)6(CH3C=C(H)CHzbf-i-Pr} (1) in hexane solution for 8 h under CO atmosphere, RUZ(CO)~(M~C=C(H)CHZN(~-P~)C-O] (3) was formed in moderate yields (30%) (Figure 2). Furthermore, smallamountsofthe byproducts [Ru(CO)&and R u ~ ( C O ) ~ ( C H ~ CC(H)C(H)N===C(Me)z} were formed, as established by their spectroscopic data. In complex 3 a CO molecule has been inserted into a Ru-N bond, as has been unambiguously established by means of X-ray crystallography (vide infra). In complex 2,1OCwhich contains a four-membered azametallacycle, CO insertion in the Ru-N bond could be effected photochemically as well (Figure 2), but not thermally. The product, Ruz(CO)6[RCC(H)N(t-Bu)C=O](4), was formed almost quantitatively and was analyzed both spectroscopically and by means of an X-ray structure determination (vide infra). In order to obtain more information about the mechanism of the CO-insertion a PPh3 ligand was introduced in complex 2, thus creating asymmetry in the metal carbonyl core. Moreover, the 31P-couplingpattern facilitates the elucidation of the molecular structure by NMR spectroscopy. The thermal reaction between 2a and I equiv of PPh3 resulted in substitution of one CO ligand and Ru~(CO)~PP~,(~-P~CC(H)N-~-BU} (Sa') was obtainedin good yield (Figure 3). The molecular structure of Sa' was established by means of spectroscopic techniques (vide infra). The photochemical CO insertion reaction was performed with this PPh3substituted derivative of 2s as well. Again, CO insertion into the Ru-N bond occurred, affording complex 6a (Figure 3). T h e conversion of 20 into 6a could also be effected in one step by irradiation of a solution of 2a in the presence of 1 equiv of PPhs (Figure 3), resulting in the same isomer of 6a as was obtained via the first route. All insertion products (3, 4, 6) appeared to be thermally unstable (60 OC in heptane), giving rise to deinsertion of CO and formation of the parent compounds 1, 2, and 5, respectively. The thermal deinsertion reaction a t 60 OC could be inhibited by working under an atmosphere of CO. Molecular Structureof 3. The molecular geometry of 3 along with the adopted numbering scheme is shown in Figure 4 and selected bond lengths and bond angles are given in Table IV. By this X-ray structure determination the position of the inserted CO ligand, uiz. in the Ru(2)-N bond and not in the Ru( 1)-C(2)
CO Insertion into Ruthenium-Amido Bonds
Inorganic Chemistry, Vol. 32, No. 17, I993 3643
Table IV. Selected Bond Distances (A) and Angles (deg) for Complex 3 (with W
Ru( 1)-Ru(2) RU(~)-C(~) Ru(21-W) Ru(2)-C( 12) 0(1)-C(8) 0 ( 4 ) - ~ ( 11) 0(7)-C(4) N-CW
2.7355(13) 1.881( 11) 2.288( 10) 1.945( 14) 1.215(11) 1.13 1(17) 1.140(16) 1.523(1)
N-Ru(l)-C(Z) C(8)-Ru(2)-C( 12) Ru( 1)-N-C(4) C(4)-N-C(5) Ru(l)-C(2)-Ru(2) C(1)-C(2)-C(3) C(2)-C(3)-C(4) N-C(5)-C(7) Ru(2)-C( 8)-N
2a
81.2(3) 171.8(5) 108.5(5) 114.1(7) 78.4(3) 119.9(10) 118.5(10) 111.0(9) 108.4(5)
Ru( 1)-N Ru( I)
